I just saw this exchange between a reader and Neil in the FAQ section of The Mouse Circus website:

Q: Could you write a sequel to THE GRAVEYARD BOOK? I just finished it and I want more!A: I will, yes, but it will go to very different places—and it may not get back to the Graveyard.

Is this news to anyone else? I'm so happy he has confirmed there will be another book.

I am guessing Scotland as one possible setting, because that's where Scarlett was heading. Maybe Bod will find a different entrance to the Sleer's lair. There had to be a reason Mr. Gaiman didn't kill off all the Jacks in the first book....

I want to see Liza again! Who will take up the flint knife and the black-handled knife? Will we learn more about The Master, and why he created a three-headed beast to guard on the plain? What about the mist walkers and the high hunters who were mentioned in Miss Lupescu's lesson for Bod (p. 71): Have we seen them already, or will they appear in the second book?

i wouldn't mind seeing a book with some of the same characters, but perhaps not an actual sequel, kind of like how Anansi Boys has a character or two from American Gods, but is still not a sequel

I also saw you mention on a different thread about how there could be a sequel to The Graveyard Book, because as you stated, Kipling wrote a second Jungle Book...although there are a lot of similarities between PARTS of the Jungle Book and The Graveyard Book and it was certainly an inspiration of Mr.Gaiman's, you need to also remember when bringing up the fact that there was a second Jungle Book that both books are not novels like The Graveyard Book, they are short stories that sometimes (but not always) have the same characters. Most people don't even realise that the whole of the Jungle Book (both books) are not all about Mowgli (please note that I'm not saying that you didn't know this, I'm just stating it for other people who may read this thread and may not have know it). Half of the stories (if not more) have nothing to do with him...hell, some of them don't even take place anywhere near the Jungle (the story of the seals comes to mind...not many seals in the Jungle)

-not back with a vengeance, more like a dull thud followed by a scared wave-

A: @shelfmagazine there's a big story I'd like to tell that may have familiar characters in it. Like a Lord of the RIngs to TGB's Hobbit #tgb

Sounds great, doesn't it? Maybe the story will tell us more about the background of the cup, knife and brooch and how they came to be in the hill. Sleer as Gollum? I wouldn't mind a story focused on the Honour Guard and how they came into being. Lots of possibilities!